The present invention relates to a sensor array having a pulse echo radar.
German Published Patent Application No. 44 42 189 discusses that sensors having transmitting and receiving units for both sending and receiving data may be used in a system for measuring distance in the area surrounding motor vehicles. With the aid of the distance measurement, passive measures to protect the vehicle may be activated, for example, in the event of a head-on, side, or rear-end collision. With an exchange of the data that is acquired, an evaluation of the traffic situation may be performed, for example, for the activation of appropriate deployment systems.
Additionally, it is believed that distance may be measured using a pulse radar in which a carrier pulse having a rectangular envelope of an electromagnetic oscillation is transmitted in the gigahertz range. This carrier pulse is reflected from the target object and the target distance and, with limitations, using the Doppler effect, also the relative speed of the target object may be determined from the time of transmission of the pulse to the time of arrival of the reflected radiation. Such a measurement principle is described in A. Ludloff""s technical book, xe2x80x9cHandbuch Radar und Radarsignalverarbeitungxe2x80x9d [Handbook of Radar and Radar Signal Processing], pages 2-21 to 2-44, Vieweg Verlag, 1993.
A plurality of radar sensors for the individual conflict situations in the area surrounding the motor vehicle may be required for the reliable deployment of the passenger protection system in a motor vehicle that was mentioned at the outset. For example, early collision recognition (precrash recognition) may be required to permit timely detection of an object that constitutes a danger for the vehicle""s passengers in a collision.
In this regard, the prior radar sensors for pulse echo operations may transmit the pulses with a fixed repetition frequency, so that the pulse trains from different transmitters thus may not be distinguished. When the transmitters of a microwave radar system operate independently from one another, e.g., with a pulse repetition frequency of 6 MHz, a carrier frequency of 24 GHz, and a pulse width of approx. 350 ps, each sensor receives only object echoes of its own pulses, while the echoes of pulses from the other transmitters are either not received or received only in the form of signal noise.
German Published Patent Application No. 198 02 724 discusses a monitoring device in which coded ultrasound pulses are transmitted that may be detected with appropriate signal echo sensors. In this regard, for the sake of differentiating the pulses that are received, they may be coded previously via a random generator and then selectively analyzed accordingly.
The present invention may provide a sensor array having a pulse echo radar system in which a carrier signal of a microwave transmitter may be transmitted in the form of pulses with a specified pulse repetition frequency. This microwave signal may be reflected from a target object and the position of the target object may be calculated in a mixer circuit from the time of transmission of the pulse and the arrival of the reflected radiation. In the process, the pulses may be transmitted only with a predefined probability via a random switch so that the stochastic pulse sequences of the transmitter may be known at the receiver for analyzing the signals that are received. Through this coding the differentiation of several transmitted signals may also be provided. This and other features of the exemplary embodiments of the invention are presented in the following description and the drawings, with each of the individual features capable of being implemented by itself or severally in the form of subcombinations in the exemplary embodiment of the invention also in different fields and may represent exemplary embodiments that are desired and for which protection is claimed here.